Nice question!
I remember opening my very first intro pack with a foil
Butcher of Malakir as deck rare, it was a joy.
Then I moved on and cracked the pack which came with the deck, pulling a mono-green
Omnath, Locus of Mana! unfortunately, back in the days, I didn't play anything besides black + didn't actually understand the card, so I traded it for a sh!tton of other cards.
It isn't even my biggest MtG-related regret...